Work under way so northbound bridge can carry two lanes in each direction

ARLINGTON – Drivers will see big changes on Interstate 5 across the Stillaguamish River beginning Monday, July 7.

Later this month, contractor crews working for the Washington State Department of Transportation will begin work to replace the entire deck and some of the supporting steel framework of the southbound I-5 Stillaguamish River bridge. Both directions of traffic will use the northbound bridge while the southbound bridge deck is being replaced.

To keep traffic moving during construction, both directions of I-5 near the Stillaguamish River bridges will be reduced from three lanes to two. Concrete barriers will be installed along the northbound bridge’s centerline and median crossover lanes will be built to shift southbound traffic to the northbound bridge.

Lane reductions begin next week. The schedule is:

Monday, July 7: Two lanes of northbound I-5 closed from 10 p.m. to 5 a.m. for grinding; one lane of southbound I-5 closed at 10 p.m. for the duration of the project for median crossover lane construction.

Tuesday, July 8: Two lanes of northbound I-5 closed from 10 p.m. to 5 a.m. for striping.

Wednesday, July 9: Two lanes of northbound I-5 closed at 10 p.m. for the duration of the project for median crossover lane construction and use.

Mid to late July: Two lanes of southbound I-5 will begin to use the median crossover lanes onto the northbound roadway, adjacent to the two lanes of the northbound I-5 traffic.

November: When work is complete, traffic will be restored to separate bridges with three lanes in each direction.

The bridges are located about 10 miles north of Marysville and about 19 miles south of Mount Vernon. With fewer lanes carrying the nearly 50,000 vehicles of each direction on I-5 across the Stillaguamish River, drivers could see delays of up to 35 minutes during peak travel times.

“If people can adjust their schedule a little during construction to avoid the peak travel periods, they can get to their destinations on time and help us keep traffic moving,” said WSDOT Northwest Regional Administrator Lorena Eng.

Once two-way traffic is established on the northbound bridge in mid to late July, heavy congestion is expected during the peak hours:

Northbound I-5: 3 to 6 p.m. Thursdays and Fridays

Northbound I-5: 11 a.m. to 4 p.m. weekends

Southbound I-5: 4 to 6 p.m. Sundays

The best times to travel will be before 9 a.m. and after 8 p.m. Drivers should check traffic information, the WSDOT mobile app, or call 511 before starting their trip.

Rules of the road

While the crossover lanes are in use, lanes on the bridge will be narrowed from 12 feet to 11 feet.

The speed limit through the work zone will be reduced from 70 to 55 mph.

Each direction will have very narrow shoulders.

BicyclesBecause of the narrow shoulders, bicycles will not be allowed on I-5 between State Route 530/Pioneer Highway and 236th Street Northeast. A signed bicycle detour has been established west of the interstate via the Pioneer Highway and 236th Street Northeast.

About the bridgeThe southbound I-5 Stillaguamish River bridge was built in 1933 as part of US 99. It originally carried two lanes in each direction and later became part of I-5 when the interstate was built in the 1960s. The northbound I-5 Stillaguamish River bridge opened in 1971. This allowed each direction its own bridge, improving safety and traffic flow on this section of I-5.